Introduction to If Else Statement
Decision Construct: - An Introduction
They
provide the facility to specify the certain condition in a program and
associate a set of statements with that condition. These conditions are
evaluated during the execution of program.
These
conditions must return a Boolean value true or false. The associated group of
statements is executed if the given condition is true.
If
the given condition is false it skips the associated group of statements and
executes the remaining statements of a program.
C language
provides three Decision constructs. They are:
i].If Statement
ii].Switch…case Statement
iii].Conditional Statement
1].if Statement
If statement is very simple decision making
statement in ‘C’ language. It allows the user to control the flow of execution
with the help of a condition and transfer the control to particular direction.
This statement divide the program into two
section one for true condition and other for false condition. Thus it is a
basically two way decision statement.
Generally if statement has the following forms:
-
i).
Simple IF statement
ii).If
…Else statement
iii). If
Else if statement
iv). Nested
if
i).
Simple IF statement
If
statement is a very simple decision making statement in ‘C’ language. The
general form of the if statement
is
{
statement 1
. . . .
. . .
. . . . . . .
statement N
}
The
if statement consists of two parts:-
a).Condition:-The
condition is a Boolean expression that must returns true (nonzero) or false
(zero) value. We can include any relational operators in condition such as
<, >, <=, >=, = = (for equality).
b).Body:-The
Body consists of one or more statements enclosed with in curly braces ({…..}).If
you want to execute only one statement, opening and closing braces are not
required.
It executes the condition first. If the
condition return true then the statements following the if are executed. If the
given condition is false then it skips the statements following the if and
executes the statements which are written after the if
WAP to input a number and convert it into absolute
value.
#include<stdio.h>
#include<conio.h>
void main()
{
int Num;
clrscr();
printf("enter a
Number");
scanf("%i",&Num);
if(Num<0)
{
Num=Num * -1;
}
printf("The absolute value is%i",
Num);
getch();
}
ii).If …Else
statement
It is an advance form
of simple if statement. This statement
will be used when we want to perform one operation when the given condition is
true and another operation when the given condition is false. The general form
of the if else statement is
if (condition)
{
Statement
. . . . . .
Statement N
}
else
{
Statement 1
. . . . . .
Statement
N
}
When the condition
return boolean true it execute the statements following the if statement. These
set of statements are called true-block.
When the condition
return boolean false it execute the statements following the if else statement.
These set of statements are called false-block.
After the execution of
true of false block control is transferred out of if. . .else statement. Note that the ‘C’ compiler executes either
true-block or false-block, but not both at the same time.
WAP to input a number from the user and check it is
negative or positive.
#include<stdio.h>
#include<conio.h>
void main()
{ int
Num;
clrscr();
printf("Enter
a Number :");
scanf("%i",&Num);
if(Num>0)
{
printf("It is positive Number ");
}
else
{
printf("It
is Negative Number");
}
getch();
}
WAP to input a number from the user and check it is even
or odd.
#include<stdio.h>
#include<conio.h>
void main()
{
int Num1;
clrscr();
printf("enter
a number");
scanf("%i",&Num1);
if(Num1%2==0)
{
printf("%i is even",Num1)'
}
else
{
printf("%i is odd",Num1);
}
getch();
}
Write a program to input two numbers and display
largest number.
#include<stdio.h>
#include<conio.h>
void main()
{
int
N1,N2;
clrscr();
printf("Enter
two Number :");
scanf("%i%i",&N1,&N2);
if(N1>N2)
{
printf("%i
is largest then %i",N1,N2);
}
else
{
printf("%i
is largest then %i",N2,N1);
}
getch();
}
Write a program to input a year from the user and
check it is leap year or not.
#include<stdio.h>
#include<conio.h>
void main()
{
int Y;
clrscr();
printf("Enter
a Year :");
scanf
("%i",&Y);
if(Y%4==0)
{
printf("It's
a leap year");
}
else
{
printf("It's
not aleap year");
}
getch();
}
Write a program to input a character from the user and
change its case.
#include<stdio.h>
#include<conio.h>
void main()
{
char
ch;
clrscr();
printf("Enter
a character :");
scanf("%c",&ch);
if(ch>=97
&& ch<=122)
{
ch=ch-32;
}
else
{
ch=ch+32;
}
printf("After
case change :%c",ch);
getch();
}
WAP to input a value and check it whether it is alphabet
or not
#include<stdio.h>
#include<conio.h>
void main()
{
char
v;
clrscr();
printf("enter
a value");
scanf("%c",&v);
if(v>='a'&&v<='z')
printf("alphabed");
else
printf("not
alphabed");
getch();
}
WAP to input a value and check it whether it is
decimal number or not
#include<stdio.h>
#include<conio.h>
void main()
{
char v;
clrscr();
printf("Enter a Value");
scanf("%c",&v);
if(v>=48&&v<=57)
{
printf("Decimal Number");
}
else
{
printf("Not a decimal
number");
}
getch();
}
Write a program to enter quantity and price and offer
15 % discount if quantity is more then 1000.
#include<stdio.h>
#include<conio.h>
void main()
{
float p, amt,dis,pay;
int qty;
clrscr();
printf("enter qty and
price");
scanf("%i%f",&qty,&p);
amt=qty*p;
if(amt>100)
{
dis=amt*.15;
}
else
{
dis=0;
}
pay=amt-dis;
printf("Total
payable amount is %f",pay);
getch();
}
Write a program to calculate gross salary according to
the following conditions
Case
1: - basic < Rs. 1500, then HRA=10% of basic salary and DA=90% of basic
salary.
Case 2:- basic >= Rs. 1500, then HRA = Rs. 500 and
DA = 98% of basic salary.
#include<stdio.h>
#include<conio.h>
void main()
{
float
bs, gs, da, hra;
clrscr();
printf
("Enter basic salary:");
scanf
("%f", &bs);
if
(bs<1500)
{
hra=bs*10/100;
da=bs*90/100;
}
else
{
hra=500;
da=bs*98/100;
}
gs=bs
+ hra + da;
printf
("gross salary = Rs. %f", gs);
getch();
}
iii). If Else
if statement
In if-else statement when the given
condition is false, the compiler automatically execute the else part. If we
want to execute else part based on a condition then we must use the if. . .else if statement. The general
form of if …else if statement is
if (condition)
{
Statement
1
. . . .
.
Statement
N
}
else if(condition)
{
Statement
1
. . . .
. .
Statement
N
}
. . . . . . . .
.
. . . . . . . .
.
else
{
Statement
1
. . . . . .
Statement
N
}
If the given condition if true it
execute the set of statements following the if statement but if the given
condition is false, the control is transferred to the else if statement.
Compiler again checks the condition here.
If the given condition is true,
compiler execute the statements following the else if statement but if the condition is false compiler transfer
the control next else if statement.
This process is continue until compiler encounter else if statement.
When all the condition is false,
compiler execute the set of statements following the else statement.
WAP to input a number and check it whether it
positive, negative or zero.
#include<stdio.h>
#include<conio.h>
void main()
{
int
Num;
clrscr();
printf("Enter
a number");
scanf("%i",&Num);
if(num>0)
{
printf("Positive
Number");
}
else if(Num<0)
{
printf("Negative Number");
}
else
{
printf("Zero");
}
getch();
}
iv). Nested if
When a if statement
contain another if statement. Such form of if statement is called nested if. The if statement which
contains another if statement is called parent/outer if. The if statement which
is inside another if statement is called child/Inner if statement.
If the parent if condition is true, the
control is transfer to the child if. After
execution of child if/child else part, the control is transferred to the outside
of parent if.
If the parent If
condition is false, the control is transferred to the parent else. After
execution of parent else statements, control is transferred outside the parent
if-else.
The general form of nested if
if
(condition)
{
if (condition)
{
Statement
1
}
else
{
Statement
1
}
}
else
{
Statement 1
Statement
N
}
Statement
X
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